Place the coffee in a shallow dish. Working with half the panettone fingers for the first layer, quickly dip each one in the coffee then lay them, side by side, in bottom of 9 x 13-in. (3-L) baking dish (or after laying panettone fingers in dish, brush with coffee). Spread half the mascarpone mixture evenly over top. Repeat the two layers once more. Finely grate chocolate overtop.